The present invention relates to electrical switchgear, and more particularly, to an adapter system and method for retrofitting existing switchgear with new, removable power circuit breakers.
Many types of low- and medium-voltage switchgear systems use power circuit breakers that can be withdrawn for maintenance. Power circuit breakers from various manufacturers are not interchangeable, and as the manufacturers have eliminated older products and introduced new technologies, the new products have not maintained compatibility with existing switchgear. The result is that many aging switchgear installations have power circuit breakers that are costly or impractical to maintain. Complete replacement of switchgear is very expensive and requires significant downtime. In the past, upgrading of obsolete circuit breakers was accomplished by significantly modifying a new circuit breaker to fit the switchgear cell, or by modifying the switchgear cell to accept a new breaker.
The current art for circuit breaker retrofits is time-consuming and costly, and may also impact customer system downtime for initial installation as well as on-going reliability issues. One conventional approach is based on adapting a new replacement breaker cradle to the existing switchgear cell by using a “cradle-within-a-cradle” approach. This requires a means of inserting, connecting and supporting the new cradle to existing primary and secondary parts inside the switchgear. This process requires additional space that complicates dielectric and heat run considerations, places an additional layer of interface that impacts reliability by creating additional points of failure for the racking system, increases susceptibility to high momentary currents, and increases material costs. A second approach has been to simply remove the interrupters and operating mechanism from the existing breaker, refurbish and reuse many of the parts, and adapt a new fixed-mount breaker to the existing withdrawal assembly. Another version of this approach is to adapt a new replacement breaker to the existing cell by recreating the existing racking and connection schemes around a fixed-mount version of the new breaker. These processes complicate the interlocking and auxiliary contact functions, and require extensive custom design work and materials.
It would therefore be desirable, if a solution were available to replace an allow a new circuit breaker to be used in an existing switchgear breaker compartment, without the need to significantly modify either component. Such a solution would help to minimize de-energization and load interruption. The present invention addresses this need.